Self-inflating sleeping pads are portable mattresses used for camping, backpacking, mountaineering, rock climbing, biking and other activities where gear needs to be light and packed into a small space, such as a backpack or a car trunk. Self-inflating sleeping pads are available in a wide variety of sizes, thicknesses, shapes and materials. Construction materials and specifications determine the comfort, weight, size, warmth and durability of the pad.
Function
Self-inflating sleeping pads are filled with open-cell foam that compresses when the pad is rolled for packing. A valve permits air to enter the pad when the valve is opened, allowing the foam to decompress, inflating the pad. The valve is closed when the pad is rolled for packing or inflated for use, making the pad airtight. Self-inflating sleeping pads should be inflated for storage. If the pad is stored rolled and compressed, the insulation may lose its ability to decompress, and the pad will not self-inflate.
Construction
Self-inflating sleeping pads are airtight and water-proof when the valve is closed. They are made from open-cell foam sandwiched between two sheets of fabric that are sealed along the edges. A two-way valve is situated at the top corner of the pad.
Materials
The top and bottom fabrics are coated polyester, nylon or a combination of both. Durable rip-stop fabrics are often used for higher quality pads. The insulation is a sheet of open-cell foam, which may be solid and flat, or have holes punched in it to save weight. The valve is plastic or metal.
Size
Sleeping pads are usually designed for one person. Most pads are 20 inches wide, but wider and double pads are available from some manufacturers. Pads come in a variety of lengths, from half-length---around 48 inches---to full-length---72 inches or more.Half-, 2/3- and 3/4-length pads are popular with backpackers because they are significantly lighter than full-length pads. Thickness varies from 1/2 inch up to 2 inches or more.
Shape
"Luxury" base camp and car camping pads are rectangular and generally come in full-length. Small, lightweight pads designed for backpacking, biking and other activities where weight and space are at a premium, are often shaped to trim off extraneous padding, featuring rounded-corners or tapered sides. Mummy-shaped pads are rectangular through the torso area, tapering from the hips to the feet and from the shoulders to the head.
Warmth
Sleeping pads are typically rated as three-season---spring through autumn---or four-season---warm enough for winter. The pad specifications often include the "R-Value" rating the efficiency of the pad's insulation, as well as a temperature comfort range. The warmth of the pad is dependent on the thickness and the insulation used.
Benefits
Self-inflating sleeping pads pack smaller than closed-cell pads, which do not compress. Self-inflating pack lighter and smaller than air mattresses, and do not require a special pump to inflate the pad. Traditional air mattresses do not hold warmth as well as self-inflating pads, may lose pressure as the outside temperatures drop during the night and are prone to punctures and leaks.
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